Key learnings from Institute for Clinical and Economic Review's real-world evidence reassessment pilot.

Health technology assessment (HTA) agencies are considering adopting a lifecycle approach to assessments to address uncertainties in the evidence base at launch and to revisit the clinical and economic value of therapies in a dynamic clinical landscape. For reassessments of therapies post launch, HTA agencies are looking to real-world evidence (RWE) to enhance the clinical and economic evidence base, though challenges and concerns in using RWE in decision-making exists. Stakeholders are embarking on demonstration projects to address the challenges and concerns and to further define when and how RWE can be used in HTA decision making. The Institute for Clinical and Economic Review piloted a 24-month observational RWE reassessment. Key learnings from this pilot include identifying the benefits and challenges with using RWE in reassessments and considerations on prioritizing and selecting topics relevant for RWE updates.

Electrospray ionization enters the final frontier: Mass spectrometry's role in understanding electrospray thrusters and their plumes.

Electrospray thrusters using ionic liquid (IL)-based propellants are quickly gaining popularity in spacecraft design. Mass spectrometry is especially well-suited to provide important knowledge on the fundamentals of how these systems work and on evaluating their efficiencies and impacts, given that the operating principles of electrospray thrusters closely mimics the mass spectrometry experiment - in both ions are generated by electrospray and then enter a vacuum. Here, electrospray thruster technology and IL-based propellants are briefly introduced. This introduction is then followed by a discussion of mass spectrometry's current contribution to the study of IL-based electrospray thrusters - with a focus on electrospray, dissociation, and spectroscopy studies - and a brief discussion of areas ripe for immediate contributions from the mass spectrometry community.

Theoretical and Experimental Insights into the Dissociation of 2-Hydroxyethylhydrazinium Nitrate Clusters Formed via Electrospray.

Ionic liquids are used for myriad applications, including as catalysts, solvents, and propellants. Specifically, 2-hydroxyethylhydrazinium nitrate (HEHN) has been developed as a chemical propellant for space applications. The gas-phase behavior of HEHN ions and clusters is important in understanding its potential as an electrospray thruster propellant. Here, the unimolecular dissociation pathways of two clusters are experimentally observed, and theoretical modeling of hydrogen bonding and dissociation pathways is used to help rationalize those observations. The cation/deprotonated cation cluster [HEH2 - H]+, which is observed from electrospray ionization, is calculated to be considerably more stable than the complementary cation/protonated anion adduct, [HEH + HNO3]+, which is not observed experimentally. Upon collisional activation, a larger cluster [(HEHN)2HEH]+ undergoes dissociation via loss of nitric acid at lower collision energies, as predicted theoretically. At higher collision energies, additional primary and secondary loss pathways open, including deprotonated cation loss, ion-pair loss, and double-nitric-acid loss. Taken together, these experimental and theoretical results contribute to a foundational understanding of the dissociation of protic ionic liquid clusters in the gas phase.

Effects of ESI conditions on kinetic trapping of the solution-phase protonation isomer of p-aminobenzoic acid in the gas phase.

The effects of electrospray ionization (ESI) solvent and source temperature on the relative abundance of the preferred solution-phase (N-protonated; i.e. amine) versus preferred gas-phase (O-protonated; i.e., acid) isomers of p-aminobenzoic acid (PABA) were investigated. When PABA was electrosprayed from protic solvents (i.e., methanol/water), the infrared multiple photon dissociation (IRMPD) spectrum recorded was consistent with that for O-protonation, according to both calculations and previous studies. When aprotic solvent (i.e., acetonitrile) was used, a different spectrum was recorded and was assigned to the N-protonated isomer. As the amine is the preferred protonation site in solution, this suggests that an isomerization takes place under certain conditions. Photodissociation at the diagnostic band for the O-protonated isomer (NH2 stretching mode) was used to quantify the relative contributions of each isomer to ion signal as a function of ESI conditions. For mixtures of methanol and acetonitrile, the relative contribution of the O-protonated gas-phase structure increased as a function of methanol content. Yet, substituting methanol for water resulted in a marked decrease of isomerization to the O-protonated structure. The source temperature (i.e., temperature of a heated desolvation capillary) was found to play a key role in determining the extent of isomerization, with higher temperatures yielding increased presence of gas-phase structures. These results are consistent with a protic bridge mechanism, in which the ESI droplet temperatures, dependent on endothermic desolvation and radiative heating from the capillary, may determine the isomerization yield.

H2SO4 and SO3 transfer reactions in a sulfopeptide-basic peptide complex.

We report on the intermolecular transfer of sulfuric acid (H2SO4) and sulfur trioxide (SO3) from an acidic sulfopeptide (sSE) to a basic peptide (R3); this is achieved by subjecting a noncovalent complex of sSE + R3 to collisional activation in a quadrupole ion trap. The product ions resulting from the sulfo-group transfers were characterized by MS(3) experiments. Peak assignments were additionally supported by isotope-labeling and energy-resolved collision induced dissiciation (CID) experiments. The observed reactions and their potential implications for proteomics and post-translational modification discovery experiments are discussed.

Peptide fragmentation products in mass spectrometry probed by infrared spectroscopy.

Vibrational spectroscopy offers detailed insights, by virtue of diagnostic infrared bands, into the chemical structures and moieties which are formed during peptide fragmentation inside mass spectrometers. Over the past few years, IRMPD spectroscopy has led to a greatly improved understanding of the chemistry that takes place during collision-induced dissociation (CID) of protonated peptides. For instance, the rearrangement chemistry of b- and a-type ions, which is relevant in sequence scrambling pathways, has been directly confirmed with the technique. In this chapter, we provide a brief background on peptide fragmentation chemistry, and give an overview of areas where vibrational spectroscopy has been successfully implemented, such as CID of protonated and de-protonated peptides. We also discuss the potential of the technique for elucidating lesser-studied radical dissociation processes, such as electron capture dissociation (ECD), electron transfer dissociation (ETD), and laser photodissociation.

Using claims data to predict dependency in activities of daily living as a proxy for frailty.

PURPOSE: Estimating drug effectiveness and safety among older adults in population-based studies using administrative health care claims can be hampered by unmeasured confounding as a result of frailty. A claims-based algorithm that identifies patients likely to be dependent, a proxy for frailty, may improve confounding control. Our objective was to develop an algorithm to predict dependency in activities of daily living (ADL) in a sample of Medicare beneficiaries. METHODS: Community-dwelling respondents to the 2006 Medicare Current Beneficiary Survey, >65 years old, with Medicare Part A, B, home health, and hospice claims were included. ADL dependency was defined as needing help with bathing, eating, walking, dressing, toileting, or transferring. Potential predictors were demographics, International Classification of Diseases, Ninth Revision Clinical Modification diagnosis/procedure and durable medical equipment codes for frailty-associated conditions. Multivariable logistic regression was used to predict ADL dependency. Cox models estimated hazard ratios for death as a function of observed and predicted ADL dependency. RESULTS: Of 6391 respondents, 57% were female, 88% white, and 38% were ≥80. The prevalence of ADL dependency was 9.5%. Strong predictors of ADL dependency were charges for a home hospital bed (OR = 5.44, 95%CI = 3.28-9.03) and wheelchair (OR = 3.91, 95%CI = 2.78-5.51). The c-statistic of the final model was 0.845. Model-predicted ADL dependency of 20% or greater was associated with a hazard ratio for death of 3.19 (95%CI: 2.78, 3.68). CONCLUSIONS: An algorithm for predicting ADL dependency using health care claims was developed to measure some aspects of frailty. Accounting for variation in frailty among older adults could lead to more valid conclusions about treatment use, safety, and effectiveness.

Observational studies of the association between glucose-lowering medications and cardiovascular outcomes: addressing methodological limitations.

BACKGROUND: Recent years have witnessed a growing body of observational literature on the association between glucose-lowering treatments and cardiovascular disease. However, many of the studies are based on designs or analyses that inadequately address the methodological challenges involved. METHODS: We reviewed recent observational literature on the association between glucose-lowering medications and cardiovascular outcomes and assessed the design and analysis methods used, with a focus on their ability to address specific methodological challenges. We describe and illustrate these methodological issues and their impact on observed associations, providing examples from the reviewed literature. We suggest approaches that may be employed to manage these methodological challenges. RESULTS: From the evaluation of 81 publications of observational investigations assessing the association between glucose-lowering treatments and cardiovascular outcomes, we identified the following methodological challenges: 1) handling of temporality in administrative databases; 2) handling of risks that vary with time and treatment duration; 3) definitions of the exposure risk window; 4) handling of exposures that change over time; and 5) handling of confounding by indication. Most of these methodological challenges may be suitably addressed through application of appropriate methods. CONCLUSIONS/INTERPRETATION: Observational research plays an increasingly important role in the evaluation of the clinical effects of diabetes treatment. Implementation of appropriate research methods holds the promise of reducing the potential for spurious findings and the risk that the spurious findings will mislead the medical community about risks and benefits of diabetes medications.

Differentiating sulfopeptide and phosphopeptide ions via resonant infrared photodissociation.

The post-translational modifications sulfation and phosphorylation pose special challenges to mass spectral analysis due to their isobaric nature and their lability in the gas phase, as both types of peptides dissociate through similar channels upon collisional activation. Here, we present resonant infrared photodissociation based on diagnostic sulfate and phosphate OH stretches, as a means to differentiate sulfated from phosphorylated peptides within the framework of a mass spectrometry platform. The approach is demonstrated for a number of tyrosine-containing peptides, ranging from dipeptides (YG, pYG, and sYG) over tripeptides (GYR, GpYR, and GsYR), to more biologically relevant enkephalin peptides (YGGFL, pYGGFL, and sYGGFL). In all cases, the diagnostic ranges for sulfate OH stretches are established as 3580-3600 cm(-1) and can thus be distinguished from other characteristic hydrogen stretches, such as carboxylic acid OH, alcohol OH, and phosphate OH stretches.

Alpha-1 acid glycoprotein reduces hepatic leukocyte recruitment in murine models of either early endotoxemia or early sepsis.

OBJECTIVE: To characterize the effect of systemically administered AGP on early leukocyte recruitment in the livers of endotoxemic or septic mice and to determine whether this is influenced by LPS sequestration. METHODS: Endotoxemia was induced in C57Bl/6 mice via intraperitoneal injection of LPS. Sepsis was induced in mice by cecal ligation and perforation. AGP (165 mg/kg) or saline (20 mL/kg) or HAS (200 mg/kg) was administered immediately after surgery or LPS injection and the hepatic microcirculation was examined by intravital microscopy at four hour. RESULTS: Leukocyte adhesion in the PSV was reduced by treatment with AGP in mice subjected to either LPS or CLP protocols compared to either saline or HAS treatment. AGP-treated mice also had significantly higher sinusoidal flow in both models. Pre-incubation of LPS with AGP reduced the ability of LPS to recruit leukocytes to the liver microcirculation. CONCLUSIONS: AGP was more effective in limiting hepatic inflammation and maintaining perfusion than saline or HAS, in both endotoxemic and septic mice. AGP sequestration of LPS may contribute to its anti-inflammatory effects.

Trends in insulin initiation and treatment intensification among patients with type 2 diabetes.

BACKGROUND: Many patients with type 2 diabetes eventually require insulin, yet little is known about the patterns and quality of pharmacologic care received following insulin initiation. Guidelines from the American Diabetes Association and the European Association for the Study of Diabetes recommend that insulin secretagogues such as sulfonylureas be discontinued at the time of insulin initiation to reduce the risk of hypoglycemia, and that treatment be intensified if HbA1c levels remain above-target 3 months after insulin initiation. OBJECTIVE: To describe pharmacologic treatment patterns over time among adults initiating insulin and/or intensifying insulin treatment. DESIGN: Observational study. SUBJECTS: A large commercially insured population of adult patients without recorded type 1 diabetes who initiated insulin. MAIN MEASURES: We evaluated changes in non-insulin antidiabetic medication use during the 120 days immediately following insulin initiation, rates of increase in insulin dose and/or dosing frequency during the 270 days following an insulin initiation treatment period of 90 days, and rates of insulin discontinuation. KEY RESULTS: Seven thousand, nine hundred and thirty-two patients initiated insulin during 2003-2008, with the majority (61 %) initiating basal insulin only. Metformin (55 %), sulfonylureas (39 %), and thiazolidinediones (30 %) were commonly used prior to insulin initiation. Metformin was continued by 64 % of patients following mixed or mealtime insulin initiation; the continuation rate was nearly as high for sulfonylureas (58 %). Insulin dose and/or dosing frequency increased among 22.9 % of patients. Insulin was discontinued by 27 % of patients. CONCLUSIONS: We found evidence of substantial departures from guideline-recommended pharmacotherapy. Insulin secretagogues were frequently co-prescribed with insulin. The majority of patients had no evidence of treatment intensification following insulin initiation, although this finding is difficult to interpret without HbA1c levels. While each patient's care should be individualized, our data suggest that the quality of care following insulin initiation can be improved.

Energy-Resolved In-Source Collison-Induced Dissociation for Isomer Discrimination.

While mass spectrometry remains a gold-standard tool for analyte detection, characterization, and quantitation, isomer differentiation is often a challenge. Tandem mass spectrometry is a common approach to increase the selectivity of mass spectrometry and energy-resolved measurements can provide further improvements. However, not all mass spectrometers, especially those that are very compact and affordable, are amenable to such experiments. For instance, single-stage mass spectrometers with soft ionization provide no dissociation information and quadrupole ion trap instruments with resonant excitation do not necessarily provide as informative of energy-resolved curves, for instance when extensive sequential dissociation is responsible for much of the "fingerprint". In-source collision-induced dissociation (IS-CID) is one approach to overcoming these barriers to exploit the analytical selectivity of energy-resolved CID without the need for additional instrumentation; this approach could broaden the reach of these selectivity gains to additional user bases (e.g., educational settings, field portable devices). Here, we specifically investigate energy-resolved IS-CID with the goal of (1) comparing between energy-resolved appearance curves measured with true tandem mass spectrometry on a quadrupole time-of-flight instrument and those obtained using IS-CID, (2) evaluating the approach as a means of differentiating isomers/isobar sets, especially those with similar dissociation patterns, and (3) exploring additional analytical considerations relevant to method development and implementation. This proof-of-concept work establishes the analytical potential of this approach, opening doors for future method development for specific applications.

Estimation using all available covariate information versus a fixed look-back window for dichotomous covariates.

PURPOSE: When using claims data, dichotomous covariates (C) are often assumed to be absent unless a claim for the condition is observed. When available historical data differs among subjects, investigators must choose between using all available historical data versus data from a fixed window to assess C. Our purpose was to compare estimation under these two approaches. METHODS: We simulated cohorts of 20,000 subjects with dichotomous variables representing exposure (E), outcome (D), and a single time-invariant C, as well as varying availability of historical data. C was operationally defined under each paradigm and used to estimate the adjusted risk ratio of E on D via Mantel-Haenszel methods. RESULTS: In the base case scenario, less bias and lower mean square error were observed using all available information compared with a fixed window; differences were magnified at higher modeled confounder strength. Upon introduction of an unmeasured covariate (F), the all-available approach remained less biased in most circumstances and rendered estimates that better approximated those that were adjusted for the true (modeled) value of C in all instances. CONCLUSIONS: In most instances considered, operationally defining time-invariant dichotomous C based on all available historical data, rather than on data observed over a commonly shared fixed historical window, results in less biased estimates.

Further exploration of the collision-induced dissociation of select beta blockers: Acebutolol, atenolol, bisoprolol, carteolol, and labetalol.

Beta blockers are a class of drugs commonly used to treat heart-related diseases; they are also regulated under the World Anti-Doping Agency. Tandem mass spectrometry is often used in the pharmaceutical industry, clinical analysis laboratory, and antidoping laboratory for detection and characterization of drugs and their metabolites. A deeper chemical understanding of dissociation pathways may eventually lead to an improved ability to predict tandem mass spectra of compounds based strictly on their chemical structure (or vice versa), which is especially important for characterization of unknowns such as emerging designer drugs or novel metabolites. In addition to providing insights into dissociation pathways, the use of energy-resolved breakdown curves can produce improved selectivity and lend insights into optimal fragmentation conditions for liquid chromatography-tandem mass spectrometry LC-MS/MS workflows. Here, we perform energy-resolved collision cell and multistage ion trap collision-induced dissociation-mass spectrometry (CID-MS) experiments, along with complementary density functional theory calculations, on five beta blockers (acebutolol, atenolol, bisoprolol, carteolol, and labetalol), to better understand the details of the pathways giving rise to the observed MS/MS patterns. Results from this work are contextualized within previously reported literature on these compounds. New insights into the formation of the characteristic product ion m/z 116 and the pathway leading to characteristic loss of 77 u are highlighted. We also present comparisons of breakdown curves obtained via qToF, quadrupole ion trap, and in-source CID, allowing for differences between the data to be noted and providing a step toward allowing for improved selectivity of breakdown curves to be realized on simple instruments such as single quadrupoles or ion traps.

Elevated risk of preeclampsia in pregnant women with depression: depression or antidepressants?

A previous study suggested an increased risk of preeclampsia among women treated with selective serotonin reuptake inhibitors (SSRIs). Using population-based health-care utilization databases from British Columbia (1997-2006), the authors conducted a study of 69,448 pregnancies in women with depression. They compared risk of preeclampsia in women using SSRIs, serotonin-norepinephrine reuptake inhibitors (SNRIs), or tricyclic antidepressants (TCAs) between gestational weeks 10 and 20 with risk in depressed women not using antidepressants. Among prepregnancy antidepressant users, the authors compared the risk in women who continued antidepressants between gestational weeks 10 and 24 with the risk in those who discontinued. Relative risks and 95% confidence intervals were estimated. The risk of preeclampsia in depressed women not treated with antidepressants (2.4%) was similar to that in women without depression (2.3%). Compared with women with untreated depression, women treated with SSRI, SNRI, and TCA monotherapy had adjusted relative risks of 1.22 (95% confidence interval (CI): 0.97, 1.54), 1.95 (95% CI: 1.25, 3.03), and 3.23 (95% CI: 1.87, 5.59), respectively. Within prepregnancy antidepressant users, the relative risk for preeclampsia among continuers compared with discontinuers was 1.32 (95% CI: 0.95, 1.84) for SSRI, 3.43 (95% CI: 1.77, 6.65) for SNRI, and 3.26 (95% CI: 1.04, 10.24) for TCA monotherapy. Study results suggest that women who use antidepressants during pregnancy, especially SNRIs and TCAs, have an elevated risk of preeclampsia. These associations may reflect drug effects or more severe depression.

Screening for phosphorylated and nonphosphorylated peptides by infrared photodissociation spectroscopy.

We present an infrared laser-based mass spectrometric strategy to differentiate peptides that are phosphorylated (i.e., containing pS, pT, or pY) from those that are nonphosphorylated (i.e., containing S, T, or Y), and those peptides that have none of these moieties (i.e., containing neither pS, pT, pY nor S, T, Y). This is demonstrated for a series of tripeptides and for two larger octapeptides, showing that the diagnostic phosphate OH stretch (indicative for pS, pT, or pY) can be distinguished from the alcohol OH stretch (indicative for S, T, or Y). In addition, the infrared multiple photon dissociation (IRMPD) spectra of multiple peptide analytes are recorded simultaneously in a multiplexed fashion. This is achieved by complexing each peptide precursor with a noncovalently bound 18-crown-6 ether, which is detached upon resonant infrared photon absorption.

The increasing prevalence of atrial fibrillation among hemodialysis patients.

A half million Americans have ESRD, which puts them at high risk for cardiovascular disease and poor outcomes. Little is known about the epidemiology of atrial fibrillation among patients with ESRD. We analyzed data from annual cohorts (1992 to 2006) of prevalent hemodialysis patients from the United States Renal Data System. In each cohort, we searched 1 year of medical claims for relevant diagnosis codes to determine the prevalence of atrial fibrillation. Among 2.5 million patient observations, 7.7% had atrial fibrillation, with the prevalence increasing 3-fold from 3.5% (1992) to 10.7% (2006). The number of affected patients increased from 3620 to 23,893 (6.6-fold) during this period. Older age, male gender, and several comorbid conditions were associated with increased risk for atrial fibrillation. Compared with otherwise similar Caucasians, the prevalence of atrial fibrillation rates was substantially lower for blacks, Asians, and Native Americans. One-year mortality was twice as high among hemodialysis patients with atrial fibrillation compared with those without (39% versus 19%), and this increased risk was constant during the 15 years of the study. In conclusion, the prevalence of diagnosed atrial fibrillation among patients receiving hemodialysis in the United States is increasing, varies by race, and remains associated with substantially increased mortality. Identifying potentially modifiable risk factors for incident atrial fibrillation requires further investigation.

Infrared multiple photon dissociation (IRMPD) spectroscopy and its potential for the clinical laboratory.

Infrared multiple photon dissociation (IRMPD) spectroscopy is a powerful tool used to probe the vibrational modes-and, by extension, the structure-of an ion within an ion trap mass spectrometer. Compared to traditional FTIR spectroscopy, IRMPD spectroscopy has advantages including its sensitivity and its relative ability to handle complex mixtures. While IRMPD has historically been a technique for fundamental analyses, it is increasingly being applied in a more analytical fashion. Notable recent demonstrations pertinent to the clinical laboratory and adjacent interests include analysis of modified amino acids/residues and carbohydrates, structural elucidation (including isomeric differentiation) of metabolites, identification of novel illicit drugs, and structural studies of various biomolecules and pharmaceuticals. Improvements in analysis time, coupling to commercial instruments, and integration with separations methods are all drivers toward the realization of these analytical applications. Additional improvements in these areas, along with advances in benchtop tunable IR sources and increased cross-discipline collaboration, will continue to drive innovation and widespread adoption. The goal of this tutorial article is to briefly present the fundamentals and instrumentation of IRMPD spectroscopy, as an overview of the utility of this technique for helping to answer questions relevant to clinical analysis, and to highlight limitations to widespread adoption, as well as promising directions in which the field may be heading.

Using primary care data to assess comparative effectiveness and safety of apixaban and rivaroxaban in patients with nonvalvular atrial fibrillation in the UK: an observational cohort study.

OBJECTIVE: To compare real-world effectiveness and safety of direct oral anticoagulants (DOACs) in patients with nonvalvular atrial fibrillation (AFib) for prevention of stroke. STUDY DESIGN AND SETTING: A comparative cohort study in UK general practice data from The Health Improvement Network database. PARTICIPANTS AND INTERVENTIONS: Before matching, 5655 patients ≥18 years with nonvalvular AFib who initiated at least one DOAC between 1 July 2014 and 31 December 2020 were included. DOACs of interest included apixaban, rivaroxaban, edoxaban and dabigatran, with the primary comparison between apixaban and rivaroxaban. Initiators of DOACs were defined as new users with no record of prescription for any DOAC during 12 months before index date. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome was stroke (ischaemic or haemorrhagic). Secondary outcomes included the occurrence of all-cause mortality, myocardial infarction (MI), transient ischaemic attacks (TIA), major bleeding events and a composite angina/MI/stroke (AMS) endpoint. RESULTS: Compared with rivaroxaban, patients initiating apixaban showed similar rates of stroke (HR: 0.93; 95% CI 0.64 to 1.34), all-cause mortality (HR: 1.03; 95% CI 0.87 to 1.22), MI (HR: 0.95; 95% CI 0.54 to 1.68), TIA (HR: 1.03; 95% CI 0.61 to 1.72) and AMS (HR: 0.96; 95% CI 0.72 to 1.27). Apixaban initiators showed lower rates of major bleeding events (HR: 0.60; 95% CI 0.47 to 0.75). CONCLUSIONS: Among patients with nonvalvular AFib, apixaban was as effective as rivaroxaban in reducing rate of stroke and safer in terms of major bleeding episodes. This head-to-head comparison supports conclusions drawn from indirect comparisons of DOAC trials against warfarin and demonstrates the potential for real-world evidence to fill evidence gaps and reduce uncertainty in both health technology assessment decision-making and clinical guideline development.

High-resolution chemical imaging through tissue with an X-ray scintillator sensor.

We describe a novel method for high-resolution chemical imaging on a surface embedded in tissue. The sensor surface consists of an X-ray scintillator film coated in a thin film loaded with chemical indicator dye. A narrow scanning X-ray beam is used to excite luminescence from X-ray scintillators located within the beam. This luminescence passes through the indicator film, and the spectrum is analyzed to measure chemical concentrations at that location. A pH sensor is demonstrated with a dynamic range between pH 6-9 and noise level of 0.05 pH units using methyl-red dyed pH paper. The location of the interface between two types of scintillator films is obtained with 0.30 mm spatial resolution even though the images are highly blurred by 10 mm of chicken breast. This work has important applications for detecting pH changes on surfaces of implanted medical devices.